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Harsh cosmic rays might give astronauts brain damage on a trip to Mars

With ever-increasing interest in making humanity a multi-planet species by colonizing Mars, scientists are trying to figure out how to make the planet habitable. However, just getting people to Mars safely might be much harder than expected. A new NASA-funded study points out that radiation exposure during a long trip to Mars could give astronauts “space brain,” which is a fancy way of saying radiation-induced brain damage.

It’s easy to forget how harsh the universe can be as we sit down here, nestled inside the Earth’s protective magnetic field. There are several types of radiation that could pose a danger to humans who spend time away from Earth. There’s the solar radiation coming from our sun in the ultraviolet and x-ray range, but there’s also the much more dangerous cosmic radiation coming from all directions in deep space. This is high-energy radiation composed mostly of ionized atomic nuclei. The study focused on determining the effects of exposure to cosmic rays in the amounts you’d encounter on a trip to Mars.

The research was conducted on mice, not real astronauts. But a rodent’s neurons should respond in more or less the same way as human neurons do when exposed to radiation. The mice were exposed to radiation in the form of charged particles at the NASA Space Radiation Laboratory for six months. That’s on the low end of the expected transit time to Mars (one way) when a spacecraft is launched during one of the orbital launch windows. The researchers found much more extensive damage to brain tissue when compared with a shorter-term study conducted last year.

Examination of the rodent brain tissue following the experiment showed measurably reduced dendritic complexity — evidence that the cosmic rays killed neurons. The radiation exposure wasn’t severe enough to cause any physical discomfort, but the rodents began exhibiting the equivalent of cognitive decline and even dementia in humans. And this study didn’t even simulate the return trip, which would probably be at least another six months. Mars itself lacks a magnetic field, so it offers little protection from cosmic rays.

An underground shelter could be used to protect astronauts during the mission on Mars, but it may not be practical to shield a spacecraft heavily enough to block incoming cosmic rays. It may also be possible to generate an electromagnetic field on a spacecraft to deflect some or all of that radiation. We’re still in the early days of testing such technologies, though. That’s not great news for anyone hoping to go to Mars in the near future.

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